The present invention relates to an apparatus for preventing transmission of vibrations from one frame or platform to another. Structures of this type are needed for various reasons, for example for use in pallets for moving electronic equipment which is fragile, for seats in vehicles and, as will be explained below with regard to the preferred embodiment of this invention, in an isolation sleeper bunk for use in semi-trailer trucks.
Tractor-trailer trucks for hauling loads long distances usually have a portion of the tractor thereof which has a sleeping compartment therein. Typically these sleeping compartments are comprised merely of a space with a sheet metal floor whereby a mattress or the like can be placed on such sheet metal floor. Consequently, two drivers can be used as a team in a trucking operation whereby one of the drivers can sleep in the sleeping compartment while the other person drives, thereby keeping the truck moving for days at a time without stopping except for refueling or the like.
A problem, however, is that the sleeping conditions are not ideal. The major reason for this problem is that the vibrations of the vehicle make it extremely difficult for persons to sleep in sleeping compartments while the vehicle is moving. This problem is well-known and there have been many attempts to solve it; for example see U.S. Pat. Nos. 4,196,483; 4,144,601; 3,760,436; 3,612,599; 3,371,359; and 3,299,447. These prior art systems, however, tend to be unduly complicated, expensive to produce and not altogether ideal from the standpoint of actually preventing transmission of vibrations from semi-trailer trucks to the bed itself.
To analyze the problem, attention is directed to FIG. 1 which shows a tractor-trailer rig. For the purpose of this analysis, it is assumed that the tractor is a rigid body. Vertical translations at the axles Y.sub.1 and Y.sub.2 result in translations X.sub.t and Y.sub.t of the sleeper compartment passenger, as well as rotation about the Z.sub.t axis. The problem of the prior art is to provide a design to isolate the sleeper compartment occupant from excitations in the X.sub.t and Y.sub.t directions.
One of the problems with the devices of the prior art is that the apparatus works differently depending upon the weight of the person supported on the mattress. Consequently, there is a need for a device which will provide the required stiffness, damping and stroke to minimize the force transmitted to the occupant and which automatically adjusts the bunk position to the design height and the design for/aft position regardless of the amount of supported weight.
Another problem with prior art designs of this type is that when the tractor hits a bump in the road, the occupant tends to be launched into the air with the mattress and associated structure. Consequently, there is a need to provide a device of this type which includes an anti-launch mechanism for attenuating the tendency for an air spring system to launch the occupant following complete compression caused by a severe bump encountered by the truck.